Studies of dispersions of organic and inorganic pigments in non-aqueous media

Coates, DA

Abstract

The behaviour of pigment dispersions containing high solid
concentrations has been studied when the dispersions settled in
such a manner that the classical Stokes' Law was inoperative.
The sedimentation of the solid particles in such suspensions occurs
with the movement of an interface, and this is termed "hindered
settling" when above the interface is tne clear supernatant liquid
and below the interface is the suspended solid. The properties of
the suspensions were judged in terms of the interface's behaviour
as a function of time.
The observation of the interface's behaviour as a function of
time, was used to determine the effect of adsorbed alKyd resin [a
polyester) from xylene onto the surface of iron oxide, titanium
dioxide and alpha copper phthalocyanine had on hindered settling
parameters. The measurement of tne mass of polymer absorbed was
undertaken by infrared spectroscopy and a radio-active tracer method.
The work was concerned witn tne inorganic and organic pigments
i,i the same bulk solution and provided information about eacn pigment
in tne same solution. The hindered settling exneriments took place
at specific points on each pigtrant's alkyd resin adsorption isotherm
to provide an understanding of Darameters involved in sedimentation
equations in chemical and physical terms.

Complementary experimental techniques were necessary,
microelectrophoresis, optical and scanning electron microscopy,
which enabled a more concise understanding of changing parameters
involved in hindered settling equations. This provided
information on the effect of adsorbed alKyd resin on the
stabilisation/destabilisation of the pigment particles.
The experimental results indicated that the adsorbed alkyd
resin stabilised iron oxide by an electrical double layer mechanism,
the titanium dioxide by a ster % ic barrier mechanism and the copper
phthalocyanine was destabilised. These conclusions are for each
pigment dispersed in solutions of alKyd resin in xylene, compared
to the pigments dispersed in xylene only.
The particle diameter and particle diameter distribution of
the pigments in the settling suspensions were seen to have the
greatest effect on parameters involved in hindered equations.

Citation

Coates, D. Studies of dispersions of organic and inorganic pigments in non-aqueous media. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 1983